William d



(No Model.)

, W. D. FORBES.

Safety Valve.

No. 234,264. Patented Nov. 9,1880.

MPEFERS. FHOTO-LITHOGRAPNER. WISHINGTON. D. C.

UNITED STATES PATENT OFFICE.

WILLIAM D. FORBES, OF NEW YORK, N. Y.

SA'F ETY- VALVE.

SPECIFICATION forming part of Letters Patent No. 234,264, dated November 9, 1880.

Application filed September 14. 1880. (No model.) I

To all whom it may concern i Be it known that l, WILLIAM D. FORBES, of the city, county, and State of New York, have invented certain new and useful Improvements in Safety-Valves, of which the followin g is a specification.

The object of my invention is to dispense with the springs and weights ordinarily used in safety-valves, and to utilize the pressure of compressed air or gas as a force to resist the opening of the valve.

The invention consists in the combination, with a safety-valve, of a chamber in which air or gas may be compressed and confined, and which is provided with a flexible diaphragm through which the compressed air or gas may act upon the valve in a direction to close it against the pressure of the steam, air, or other fluid in the boiler or vessel to which the valve may be applied.

The chamber containing the diaphragm is preferably surmountedzby a cylinder or tube fitted with a piston, and suitable devices are employed for forcing the piston downward to compress the air or gas below it.

The device for actuating the piston may con sist of a second cylinder or tube, to the upper end of which the piston-rod is connected, and which fits over and has a screw-threaded connection with the first cylinder or tube, so that by turning the outer cylinder upon the inner cylinder the piston will be raised or lowered in said inner cylinder. The inner cylinder or tube may have marked upon its exterior a scale for indicating the increased pressure produced as the outer cylinder is moved downward.

The invention also consists in the combination, with the safety-valve, the chamber and diaphragm, the inner and outer cylinders, and the piston fitting said inner cylinder, of a novel form of connection between the piston and said outer cylinder, which enables the piston to be expanded to more tightly fit its cylinder from outside the outer cylinder.

In the accompanying drawings, Figure 1 represents a central vertical section of a safetyvalve embodying my invention. Fig. 2 is a side view of the two cylinders detached from other parts and showing the pressure-scale;

and Fig. 3 represents a central vertical section of a device of slightly modified form.

Similar letters of reference designate corresponding parts in all the figures.

A designates the shell or body, and B the valve proper, of an ordinary safety-valve.

The shell has in all cases two nozzles, a b, one of which, a, leads from the boiler, while the other, I), is for the escape of steam, air, or other fluid from the safety-valve.

The shell or body preferably has a third nozzle, 0, leading to the cylinder of an engine, when the valve is used in connection With a steam-engine.

U designates a chamber or frame extending above the valve shell or body, and having openings in its side,- and the stem at of the valve is provided with a disk or flange, d, which enables the valve to be raised to try it by a tool inserted through the openings in the side of the chamber 0.

D designates a chamber having a flexible bottom or diaphragm, e, the curvature of which is sufficient to give the necessary flexibility and movement, and which bears upon the top of the valve-stem (1. As here represented the chamber D is held in place by a clamping-ring, C, engaging, by means of a screw-thread, with the chamber (J.

E designates the cylinder or tube surmounting the chamber D, and having its lower end open to afford constant communication with the latter. Within the cylinder E is fitted a piston composed of two parts, F F, and an interposed flexible packing, f, and hemp, rubher, or other material. If desirable, metallic ring packing might be used, in which case the two parts F F should be constructed accordingly.

The cylinder E has formed upon it an external screw-thread, g, and G designates an outer cylinder or tube, which fits over the inner cylinder, E, and is internally screwthreaded for a large portion of its length, so as to engage with the screw-thread g.

' The piston F F is connected to the upper closetl end of the cylinder G, and hence by turning the outer cylinder upon the inner cylinder the air or gas below the piston may be compressed to any required degree, which will be indicated by the scale h upon the exterior of the cylinder E, as shown in Fig. 2. The diaphragm 0 will, of course, act upon the valve-stem d and press the valve to its seat with a force proportionate to the pressure of the air or gas.

In order to enable the piston to lock the air or gas in the chamber 1) and in the cylinder E, I provide a means for expanding the packing from outside the cylinder G. To effect this I interpose between the part F of the piston and the upper closed end of the cylinder G a tube, 1', and I connect to the part F a stem or rod,j, which extends upward through the tube 11 and the closed end of the cylinder, and is provided on the outside of said cylinder with a nut, 1;. By turning the nut is the parts F F are brought nearer together and the packingf compressed, expanded, or forced outward to tightly fill the cylinder E.

\Vhere a heavy pressure is desired I may employ, instead of the valve shown in Figs. 1 and 2, a valve of the kind shown in Fig. 3.

The chamber 1), with its diaphragm c acting on the valve-stem (I, is the same as in Fig. 1, and is adapted to be secured to a valve in the same way.

H designates a cylinderarranged above the chamber 1) and fitted with a piston, l, which may be operated by a lover, I, and link 1 Between the cylinder H and the chamber 1) is interposed a cock, J, which may be closed to confine the compressed air in the chamber D, and a check-valve, I, which prevents the air from passing backward when the piston is raised.

The chamber 1) is supplied with a gage, K, to indicate the pressure, which may be of any form other than that here shown. and it is also supplied with a pet-cock, a, which may be. opened to nicely adjust the air-pressure in the chamber 1). At each downward stroke of the piston I the air which has entered the cylinder through openings 1): is compressed and forced into the chamber 1). The piston is operated until the gage K indicates a sutiicient pressure, when the cock J is closed and the air thereby confined in the chamber 1).

Valves of my improved construction are very desirable, as they are less likely to be tampered with by a passer-by than the lever and weight, or springs commonly used, and they are also much lighter and can be transported complete, requiring only to be attached to the boiler to make them fit for operation. Their lightness is an important advantage when used upon portable and fire engines, and when so used they are much less likely to be disturbed by moving the engine from place to place.

The flexible diaphragm offers very little resistance by friction to the opening of the valve, and as it is constant it may be allowed for in constructing the scale or pressure gage.

Although the parts E and G are represented as, and preferably are, cylindrical in form, they might be tubes of other form.

What 1 claim as my invention, and desire to secure by Letters Patent, is-

1. The combination, with a safety-valve, ot' a chamber in which air or gas may be compressed and confined, and which is provided with a flexible diaphragm through which the compressed air or gas may act upon the valve in a direction to close it against the pressure of the steam, air, or other fluid in the boiler or vessel to which the valve may be applied, substantially as herein described.

2. The combination, with a safetyvalve, of a chamber having a flexible diaphragm hearing upon said valve, a cylinder or tube surmounting said chamber, a piston fitted to said cylinder or tube, and devices for forcing down said piston to compress the air below it, substantially as and for the purpose specitied.

3. The combination of an inner cylinder or tube adapted to be attached to a safety-valve casing, and having a flexible bottom or end adapted to press on the valve in a direction to close it, an outer cylinder or tube adjustably secured onto said inner cylinder or tube, a piston or plunger connected with said outer cylinder or tube and working in said inner cylinder or tube for the purpose of compressing the air therein, substantially as and for the purpose herein described.

4. The combination, with a safety-valve, of a chamber provided with a flexible diaphragm bearing upon said valve, a cylinder or tube surmountin g said chamber, a piston fitted to said cylinder or tube, an outer cylinder or tube fitting outside the first said cylinder or tube and connected with said piston, and a graduated scale upon the exterior of the inner cylinder or tube, substantially as and for the purpose specified.

5. The combination, with a safety-valve, ot' the inner cylinder or tube having a flexible bottom or end, the expanding plunger or piston, fitted to said cylinder or tube, the outer cylinder or tube screwed onto said inner cylinder or tube, a screw-connection between the said piston or plunger and outer cylinder or tube, means for expanding the said piston or plunger, and a nut applied to said screw-connection outside of said outer cylinder or tube to adjust the expansion of said piston or plunger, substantially as herein described.

6. The combination, with a safety-valve, of the externally screw-threaded inner cylinder or tube, E, the internally screw threaded outer cylinder or tube, G, the piston F F, and packing f, the tube 5, the rod or stem j, and the nut k, all substantially as specified.

WILLIAM D. FORBES.

Witnesses:

E. P. BURNHAM, JOHN R. RoLLms. 

